Isomerization catalyst, process for its preparation and use

Abstract

An isomerization catalyst characterized in that the catalyst comprises a composite carrier and platinum supported on the composite carrier, the composite carrier comprising 15.0-80.0 mass% of hydrogen type ZSM-22 zeolite, 10.0-70.0 mass% of hydrogen type ZSM-48 zeolite, 10.0-60.0 mass% of aluminum oxide based on the composite carrier. The catalyst is used for n-alkane isomerization reaction, has high activity and good stability, and can obtain higher isomer selectivity and yield, especially higher multi-branched alkane isomer selectivity and yield, and lower cracking product yield.

Description

Technical Field

[0001] This invention relates to catalysts, preparation methods, and applications thereof, and more specifically to isomerization catalysts, preparation methods, and applications thereof. Background Technology

[0002] In the oil refining industry, one important way to increase the octane number of gasoline is through isomerization, converting light straight-chain alkanes into isoalkanes. High-octane gasoline is mainly composed of olefins, aromatics, and isoalkanes. Due to increasingly stringent environmental requirements and upgraded standards for automotive gasoline, the content of olefins and aromatics in the gasoline pool is further restricted, creating an urgent need for more isoalkanes to fill the component gaps in the gasoline pool. Isomerization is a processing technology that can effectively increase the content of isoalkanes and improve fuel quality, and its application prospects are broad.

[0003] Currently, C5 / C6 isomerization technology is relatively mature both domestically and internationally. C5 / C6 isomerized oil effectively increases the octane number at the front end of the gasoline reservoir, but it also brings problems such as difficulty in controlling vapor pressure. To ensure gasoline product quality, it is necessary to produce C7 and higher carbon number isoalkanes through isomerization reactions. However, when mature C5 / C6 isomerization catalysts are applied to the isomerization reaction of C7 and higher carbon number alkanes, they cause a large number of alkane cracking reactions, resulting in a significant decrease in the selectivity and yield of isoalkanes.

[0004] C7+ isomers, obtained through isomerization of C7+ n-alkanes (C7+ n-alkanes), exhibit high octane numbers, stability, and vapor pressures, demonstrating excellent performance and economic and environmental advantages. The core of C7+ n-alkanes isomerization technology is the isomerization catalyst. An isomerization catalyst is a bifunctional catalyst, typically consisting of metals Pt and / or Pd supported on an acidic support. Molecular sieves with specific structures are commonly used supports, and different molecular sieve structures generally exhibit different reactivity and isomer product distributions.

[0005] Existing zeolite-type isomerization catalysts are generally based on twelve-membered ring macroporous zeolites. Due to their strong acidity, obtaining high isomer yields under high conversion conditions is difficult. One-dimensional ten-membered ring high-silica zeolites, on the other hand, have lower acidity and can achieve high isomer yields at high conversion rates. However, the small pore size of ten-membered ring channel zeolites limits the diffusion of reactants and products. Therefore, modifying their pore structure to improve diffusion performance is an effective means to enhance reaction performance.

[0006] ZSM-22 is a high-silica molecular sieve with a TON-type topology and one-dimensional ten-membered ring channels. ZSM-48 is a molecular sieve with an MRE-type topology and one-dimensional ten-membered ring channels along the

[100] direction. The channel diameter of ZSM-48 is slightly larger than that of ZSM-22. Both sieves allow alkane molecules to pass through and react. Both molecular sieves exhibit shape selectivity for alkane molecules. Supported metal-supported bifunctional catalysts often show good performance in hydroisomerization reactions.

[0007] CN112934251A discloses a bifunctional catalyst for the hydroisomerization of n-heptane and its preparation method. The catalyst comprises a hierarchical porous mordenite molecular sieve and a metal element with hydrogenation activity. The hierarchical porous mordenite molecular sieve is obtained by post-processing technology and has micropores of 0.58-0.70 nm and mesopores of 8-10 nm. The metal is selected from at least one of platinum, palladium, and nickel. This catalyst has better performance than conventional microporous catalysts and monofunctional catalysts, but the n-heptane conversion rate does not exceed 60.2%.

[0008] CN112934254A discloses a bifunctional catalyst for the hydroisomerization of n-heptane and its preparation method. The catalyst comprises a molecular sieve and a metal with hydrogenation function supported on the molecular sieve, wherein the molecular sieve is a ZSM-5 molecular sieve with hierarchical pores. The hierarchical molecular sieve is obtained by desilication of microporous molecular sieve and has micropores of 0.52-0.56 nm and mesopores of 8-15 nm. The metal is selected from at least one of platinum, palladium, and nickel. The preparation method of the bifunctional catalyst includes at least the following steps: (1) obtaining a hierarchical molecular sieve by desilication of microporous molecular sieve; (2) adding the hierarchical molecular sieve to a solution containing a metal element precursor, and obtaining the bifunctional catalyst by reaction, drying, and calcination. When this catalyst is used for the hydroisomerization reaction of n-heptane, the conversion rate of n-heptane is only 20.3-32.6%, and the selectivity of isoheptane is at most 21.6%, indicating that the catalyst has low activity and selectivity.

[0009] CN112661169A discloses a hierarchical ZSM-22 molecular sieve, which is prepared by introducing a silanized polymer. The specific process is as follows: (1) An aluminum source, a silicon source, and a structure-directing agent (SDA) are prepared into a ZSM-22 zeolite precursor solution according to the ratio 1Al2O3:(50-100)SiO2:(5-20)SDA:(1000-2000)H2O; (2) The precursor solution is aged at room temperature and then pre-crystallized; (3) The silanized polymer is added to the above solution; (4) Hydrothermal crystallization is performed; (5) The solid product is separated, washed, dried, and calcined to obtain the hierarchical ZSM-22 molecular sieve. This molecular sieve can be used as a hydrogenation catalyst support. Summary of the Invention

[0010] The purpose of this invention is to provide an isomerization catalyst and its preparation method. This catalyst is used for the isomerization reaction of n-alkanes, exhibiting high activity and good stability, and can achieve high isomer selectivity and yield, especially high isomer selectivity and yield of multi-branched alkanes, while achieving a low cracking product yield.

[0011] To achieve the above objectives, a first aspect of the present invention provides an isomerization catalyst, characterized in that the catalyst comprises a composite support and platinum supported on the composite support, wherein the composite support comprises 15.0-80.0% by mass of hydrogen-form ZSM-22 zeolite, 10.0-70.0% by mass of hydrogen-form ZSM-48 zeolite, and 10.0-60.0% by mass of alumina based on the composite support.

[0012] To achieve the above objectives, a second aspect of the present invention provides a method for preparing an isomerization catalyst, characterized in that the method comprises:

[0013] (1) A step of treating ZSM-22 and ZSM-48 mixed zeolite with alkali and acid to obtain alkali and acid modified hydrogen form ZSM-22 and ZSM-48 mixed zeolite; (2) A step of preparing a composite carrier containing the alkali and acid modified hydrogen form ZSM-22 and ZSM-48 mixed zeolite obtained in step (1) and alumina; (3) A step of loading metal.

[0014] To achieve the above objectives, a third aspect of the present invention provides an isomerization method comprising contacting and reacting a n-alkane with a catalyst under hydrogen-exposed conditions, characterized in that the catalyst is the catalyst of the present invention described above or the catalyst prepared by the present invention.

[0015] The isomerization catalyst provided by this invention first involves treating ZSM-22 and ZSM-48 zeolites with an alkali to alter the pore size and active site distribution on the support surface. Then, acid treatment removes impurities deposited on the support surface. Next, a binder component is mixed to form a composite support. Finally, platinum metal with dehydrogenation / hydrogenation functions is loaded onto the support. This catalyst is used for the isomerization reaction of n-alkanes, exhibiting high activity and good stability, achieving high isomer selectivity and yield, especially high selectivity and yield of multi-branched isomers, and low cracking product yield. The catalyst also has a long single-pass reaction cycle. Attached Figure Description

[0016] Figure 1 These are pore size distribution curves of the catalysts obtained in Examples 1-2 and Comparative Examples 1-4. Detailed Implementation

[0017] A first aspect of this invention provides an isomerization catalyst, characterized in that the catalyst comprises a composite support and platinum supported on the composite support, wherein the composite support comprises 15.0-80.0% by mass of hydrogen-form ZSM-22 zeolite, 10.0-70.0% by mass of hydrogen-form ZSM-48 zeolite, and 10.0-60.0% by mass of alumina based on the composite support. Preferably, the composite support contains 20.0-70.0% by mass of hydrogen-form ZSM-22 zeolite, 20.0-60.0% by mass of hydrogen-form ZSM-48 zeolite, and 10.0-55.0% by mass of alumina. The composite support is cylindrical, with a radius of 0.2-1.0 mm and a length of 0.5-5.0 mm.

[0018] Preferably, in the composite carrier, the mass ratio of hydrogen-form ZSM-22 zeolite to hydrogen-form ZSM-48 zeolite is 0.2-4, more preferably 0.3-3.3. The SiO2 / Al2O3 molar ratio of the hydrogen-form ZSM-22 zeolite is 20-200, and the SiO2 / Al2O3 molar ratio of the hydrogen-form ZSM-48 zeolite is 50-300.

[0019] Preferably, the catalyst of the present invention, based on the composite support, has a platinum content of 0.01-2.0% by mass.

[0020] The catalyst of this invention has a mesoporous pore volume of 0.25-0.80 cm³. 3 / g, preferably 0.30-0.60cm 3 The catalyst has a bimodal pore size distribution, with most probable pore diameters of 3.0-4.5 nm and 20.0-45.5 nm, preferably 3.2-4.0 nm and 22.0-44.5 nm. The total specific surface area of ​​the catalyst is 220.0-280.0 m² / g. 2 / g, preferably 222.5-248.0m 2 / g; mesoporous specific surface area is 60.0-150.0m² 2 / g, preferably 66.5-120.0m 2 / g.

[0021] A second aspect of the present invention provides a method for preparing an isomerization catalyst, characterized in that the method comprises:

[0022] (1) A step of treating ZSM-22 and ZSM-48 mixed zeolite with alkali and acid to obtain alkali and acid modified hydrogen form ZSM-22 and ZSM-48 mixed zeolite; (2) A step of preparing a composite carrier containing the alkali and acid modified hydrogen form ZSM-22 and ZSM-48 mixed zeolite obtained in step (1) and alumina; (3) A step of loading platinum.

[0023] This invention provides a catalyst prepared by loading an appropriate amount of platinum onto a composite support. The active components of the composite support are hydrogen-form ZSM-22 zeolite and hydrogen-form ZSM-48 zeolite. The ZSM-22 and ZSM-48 zeolites in the catalyst of this invention have weak acidity, which can mitigate the tendency of reactants to crack. Alkali treatment modification can expand the pores of the zeolite or form hierarchical pores, which spatially favors the formation of multi-branched isomers with larger kinetic diameters, and also increases the number of active sites on the catalyst surface. Acid treatment modification effectively removes deposits on the molecular sieve surface, improving its acid distribution and isomerization performance. The catalyst prepared from the above materials exhibits high selectivity and yield of isomers, especially multi-branched isomers, and low yield of cracking products when used in isomerization reactions.

[0024] In the method for preparing the catalyst described in the invention, step (1) is more specifically described as follows:

[0025] (a) Add the ZSM-22 and ZSM-48 mixed zeolite to the alkaline solution to make it fully contact the alkaline solution, filter it, wash the resulting solid with water and dry it;

[0026] (b) The zeolite obtained in step (a) is added to the ammonium salt solution to allow it to fully contact the ammonium salt solution for ion exchange and filtration. The resulting solid is washed with water, dried, and calcined to obtain alkali-modified hydrogen-form ZSM-22 and ZSM-48 mixed zeolite.

[0027] (c) The alkali-treated modified hydrogen form ZSM-22 and ZSM-48 mixed zeolite obtained in step (b) is added to an acid solution to make it fully contact with the acid solution. After filtration, the resulting solid is washed with water, dried and calcined to obtain alkali- and acid-treated hydrogen form ZSM-22 and ZSM-48 mixed zeolite.

[0028] In step (a), the method of fully contacting the sample with the alkaline solution involves stirring at a temperature of 50-90°C for 1-5 hours; the drying method involves drying at a temperature of 80-150°C for 1-5 hours. The alkaline solution is selected from at least one of sodium hydroxide solution, potassium hydroxide solution, tetraalkylammonium hydroxide solution, sodium carbonate solution, potassium carbonate solution, or ammonia water, and its concentration is 0.05-0.6 mol / L, preferably 0.1-0.4 mol / L. The mass ratio of the ZSM-22 and ZSM-48 mixed zeolite to the alkaline solution is 0.01-0.8.

[0029] In step (b), the ammonium salt solution is an NH4Cl or NH4NO3 solution with a concentration of 0.05-4 mol / L. The method for ensuring sufficient contact with the ammonium salt solution is stirring at 20-90°C for 1-24 hours; the drying process is carried out at 80-150°C for 1-5 hours; and the calcination process is carried out at 450-650°C for 2-6 hours. The mass ratio of the zeolite obtained in step (a) to the ammonium salt solution is 0.01-0.6.

[0030] In step (c), the acid solution is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, trifluoroacetic acid, oxalic acid, acetic acid, citric acid, tartaric acid, and malic acid solutions, and the concentration of the acid solution is 0.05-6.0 mol / L. The method of ensuring sufficient contact with the acid solution is stirring at a temperature of 60-200℃ for 4-12 hours; the drying method is drying at a temperature of 80-150℃ for 1-5 hours; and the calcination method is calcining at a temperature of 450-650℃ for 2-6 hours. In step (b), the mass ratio of the alkali-modified hydrogen-form ZSM-22 and ZSM-48 mixed zeolite obtained to the acid solution is 0.01-0.8.

[0031] In the method for preparing the catalyst described in the invention, step (2) is more specifically described as follows:

[0032] The pseudoboehmite powder was thoroughly mixed with the alkali- and acid-modified hydrogen-form ZSM-22 and ZSM-48 mixed zeolites obtained in step (1), and an appropriate amount of acid solution was added. The mixture was kneaded evenly, extruded into strips, dried, and calcined to obtain a composite carrier. The amount of pseudoboehmite powder added was such that the dry-basis alumina content in the composite carrier was 10.0-60.0% by mass, based on the mass of the composite carrier.

[0033] The acid solution is an inorganic or organic acid solution. The inorganic acid is selected from nitric acid and hydrochloric acid, and the organic acid is selected from acetic acid and formic acid. The concentration of the acid solution is 0.1-5% by mass. The mass ratio of the acid solution to boehmite powder is 0.5-2. The kneading is performed 1-5 times. The drying process involves first drying at 30-100℃ for 2-6 hours, and then drying at 110-150℃ for 2-24 hours. The calcination temperature is 500-650℃, and the time is 2-8 hours.

[0034] In the method for preparing the catalyst described in the invention, step (3) is more specifically described as follows: impregnating, drying, calcining, and reducing the composite support prepared in step (2) with a solution containing a platinum compound. The concentration of platinum in the solution containing the platinum compound is 0.02-2.0% by mass, and the platinum compound is a chloride or nitrate of platinum, preferably chloroplatinic acid. The liquid / solid mass ratio of the impregnation is 0.5-1.3, the impregnation temperature is 10-50°C, and the time is 1-4 hours, preferably 2-3 hours. The drying temperature is 110-150°C, and the time is 2-24 hours; the calcination temperature is 500-700°C, and the time is 0.5-8 hours, preferably 4-6 hours. The reducing gas is H2, and the volume hourly space velocity is 1.0-10.0 h⁻¹. -1 The temperature is 400-600℃, preferably 420-500℃, and the time is 0.5-8 hours, preferably 2-4 hours.

[0035] The catalyst preparation method of this invention involves modifying ZSM-22 and ZSM-48 zeolites with alkali and acid. This improves the pore size distribution and surface active center distribution of the catalyst support zeolite, introducing a mesoporous channel structure while maintaining the original pore structure of the zeolite, increasing the specific surface area of ​​the zeolite, and optimizing the distribution of surface active centers. The catalyst of this invention features good stability, a long single-pass reaction cycle, and no long-term carbon buildup or deactivation.

[0036] The third aspect of the present invention provides an isomerization method that enables n-alkanes to undergo a series of reactions such as dehydrogenation, skeletal isomerization, and hydrogenation under the action of a catalyst to generate liquid products containing isoalkanes.

[0037] The isomerization method provided by this invention involves contacting and reacting n-alkanes with the catalyst described in this invention or the catalyst prepared by the method described in this invention under hydrogen-exposed conditions. The isomerization conditions include: a temperature of 100-400℃, preferably 200-340℃; a pressure of 0.1-5.0 MPa, preferably 0.2-1.0 MPa; a hydrogen-to-oil volume ratio of 0.5-500; and a feed mass hourly space velocity (WHSV) of 0.05-10.0 h⁻¹. -1 .

[0038] The n-alkanes are C4-C12 n-alkanes, preferably C6-C8 n-alkanes, and can also be raw materials containing C4-C12 n-alkanes, such as naphtha or raffinate after aromatic extraction.

[0039] The isomerization method provided by this invention can be used in moving bed reactors or fixed bed reactors, and is particularly suitable for fixed bed reactors.

[0040] The invention is further illustrated by the following examples, but the invention is not limited thereto.

[0041] In the examples and comparative examples, the specific surface area and mesopore volume of the catalysts were determined using the ASTM D4365 method.

[0042] The instrument used was a Micromeritics AsAp2400 static nitrogen adsorption instrument.

[0043] Measurement procedure: The catalyst sample was degassed at 300℃ for 4 hours until a vacuum of 1.33 × 10⁻⁶ was reached. -2 The nitrogen gas was then brought into contact with the adsorbent at liquid nitrogen temperature (-196℃) until static adsorption equilibrium was reached. The amount of nitrogen adsorbed by the adsorbent was calculated from the difference between the nitrogen inlet flow rate and the amount remaining in the gas phase after adsorption. Then, the specific surface area and pore volume were calculated using the two-parameter BET formula, and the pore size distribution and corresponding mesopore volume were calculated using the BJH formula.

[0044] Particle size parameters were determined using ASTM D4513-11.

[0045] The most probable bore diameter parameters were determined using ASTM D4641-17.

[0046] In the following example, the feed conversion rate is calculated as follows: Feed conversion rate = (Total n-heptane feed amount - n-heptane amount in product) / Total n-heptane feed amount × 100%.

[0047] The heptane isomer selectivity is calculated as follows: heptane isomer selectivity = amount of heptane isomers produced / (total n-heptane feed amount - amount of n-heptane in the product) × 100%.

[0048] The total yield of heptane isomers is calculated as follows: Total yield of heptane isomers = Amount of heptane isomers generated × Feed conversion rate.

[0049] The yield of single-branched heptane isomers is calculated as follows: Yield of single-branched heptane isomers = Amount of single-branched heptane isomers generated × Feed conversion rate.

[0050] The yield of multi-branched heptane isomers is calculated as follows: multi-branched heptane isomer yield = amount of multi-branched heptane isomers produced × feed conversion rate.

[0051] The method for calculating the cracking product yield is: Cracking product yield = Cracking product generation amount × Feed conversion rate.

[0052] Example 1

[0053] (1) Preparation of alkali and acid-treated modified hydrogen-form ZSM-22 and ZSM-48 mixed zeolites

[0054] (a) Alkali treatment modification: 100 g of potassium-type ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 89 and 100 g of sodium-type ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 100 were mixed evenly. 3 kg of 0.3 mol / L NaOH aqueous solution was added under mechanical stirring. After mixing evenly, the mixture was stirred at 85°C for 2 hours. The mixture was filtered, and the resulting solid was washed with deionized water until the washing solution was neutral. The solid was dried at 110°C for 4 hours to obtain alkali-treated modified mixed zeolite.

[0055] (b) Ammonium exchange: Under mechanical stirring, 150 g of the alkali-treated modified mixed zeolite obtained in step (a) was subjected to three ion exchanges with 1.0 mol / L NH4Cl aqueous solution at an exchange temperature of 85 °C. The amount of NH4Cl aqueous solution used for each ammonium ion exchange was 2.25 kg. The solid obtained after ion exchange was dried at 110 °C for 4 hours and calcined at 550 °C for 3 hours to obtain alkali-treated hydrogen form ZSM-22 and ZSM-48 mixed zeolite.

[0056] (c) Acid treatment modification: Under mechanical stirring, 100 g of the ammonium-exchanged alkali-modified mixed zeolite obtained in step (b) was added to 1.5 kg of HCl solution with a concentration of 3 mol / L. After mixing evenly, the mixture was stirred at 160 °C for 5 hours. The treated sample was filtered, washed until neutral, dried at 110 °C for 4 hours, and calcined at 550 °C for 3 hours to obtain alkali- and acid-modified hydrogen form ZSM-22 and ZSM-48 mixed zeolite.

[0057] (2) Preparation of composite carrier

[0058] Take 6.7 grams of pseudoboehmite ( SB powder (alumina content of 75% by mass, the same below) was mixed with 45g of hydrogen-form ZSM-22 and ZSM-48 mixed zeolite prepared in step (1). After mixing evenly, 5g of nitric acid aqueous solution with a concentration of 1.5% by mass was added. After thorough stirring, the mixture was kneaded 3 times on an extruder and extruded into strips. The radius of the die hole of the extruder was 0.5mm. The extruded cylindrical strips were transferred to 60℃ and dried for 4 hours, then placed at 120℃ and dried for 4 hours. Finally, they were calcined at 550℃ for 4 hours and then cooled to room temperature. The long cylindrical strips were cut into cylindrical strips with a height of 2mm to make cylindrical strip composite carrier a. It contains 45% by mass of hydrogen-form ZSM-22 molecular sieve with a SiO2 / Al2O3 molar ratio of 89, 45% by mass of hydrogen-form ZSM-48 molecular sieve with a SiO2 / Al2O3 molar ratio of 100 and 10% by mass of γ-alumina.

[0059] (3) Preparation of catalyst

[0060] 45 g of the composite carrier a prepared in step (1) was placed in 37.5 g of a 0.6% by mass solution of chloroplatinic acid (produced by Bailingwei Company) and impregnated at 25°C for 3 hours. The impregnated solid was dried at 120°C for 6 hours, calcined at 500°C for 4 hours, and then reduced in a hydrogen atmosphere at 450°C for 3 hours. The volume hourly space velocity of the hydrogen treatment was 5 h⁻¹. -1 The composition of the obtained catalyst A is shown in Table 1, and its physical properties are shown in Table 2.

[0061] Example 2

[0062] The catalyst was prepared according to the method of Example 1, except that in step (1), 150 g of potassium-type ZSM-22 molecular sieve with a SiO2 / Al2O3 molar ratio of 89 and 50 g of sodium-type ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 100 were used instead of 100 g of potassium-type ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 89 and 100 g of sodium-type ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 100 to obtain cylindrical bar-shaped composite support b, which contains 67.5% by mass of hydrogen-type ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 89, 22.5% by mass of hydrogen-type ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 100 and 10% by mass of γ-alumina; the composition of the obtained catalyst B is shown in Table 1, and the physical properties are shown in Table 2.

[0063] Example 3

[0064] The catalyst was prepared according to the method of Example 1, except that in step (1), 50 g of potassium-type ZSM-22 molecular sieve with a SiO2 / Al2O3 molar ratio of 89 and 150 g of sodium-type ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 100 were used instead of 100 g of potassium-type ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 89 and 100 g of sodium-type ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 100 to obtain cylindrical bar-shaped composite support c, which contains 22.5% by mass of hydrogen-type ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 89, 67.5% by mass of hydrogen-type ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 100 and 10% by mass of γ-alumina; the composition of the obtained catalyst C is shown in Table 1, and the physical properties are shown in Table 2.

[0065] Example 4

[0066] The catalyst was prepared according to the method of Example 1, except that in step (2), 66.7 g of pseudoboehmite was taken and 50 g of the hydrogen form ZSM-22 and ZSM-48 mixed zeolite prepared in step (1) was added to it. After mixing evenly, 40 g of nitric acid aqueous solution with a concentration of 1.5% by mass was added to obtain cylindrical strip-shaped composite support d, which contains 25% by mass of hydrogen form ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 89, 25% by mass of hydrogen form ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 100 and 50% by mass of γ-alumina. The composition of the obtained catalyst D is shown in Table 1 and the physical property parameters are shown in Table 2.

[0067] Example 5

[0068] The catalyst was prepared according to the method of Example 1, except that in step (3), 37.5 g of chloroplatinic acid solution with a platinum concentration of 1.2% by mass was used instead of 37.5 g of chloroplatinic acid solution with a platinum concentration of 0.6% by mass. The composition of the resulting catalyst E is shown in Table 1, and the physical properties are shown in Table 2.

[0069] Example 6

[0070] The catalyst was prepared according to the method of Example 1, except that in step (1), potassium ZSM-22 molecular sieve with a SiO2 / Al2O3 molar ratio of 150 was used instead of potassium ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 89 to obtain cylindrical bar-shaped composite support f, which contains 45% by mass of hydrogen ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 150, 45% by mass of hydrogen ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 100 and 10% by mass of γ-alumina; in step (3), 37.5 g of chloroplatinic acid solution with a platinum concentration of 1.8% by mass was used instead of 37.5 g of chloroplatinic acid solution with a platinum concentration of 0.6% by mass. The composition of the catalyst F obtained is shown in Table 1 and the physical property parameters are shown in Table 2.

[0071] Example 7

[0072] The catalyst was prepared according to the method of Example 1, except that in step (1), sodium ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 150 was used instead of sodium ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 100 to obtain a cylindrical bar-shaped composite support g, which contains 45% by mass of hydrogen ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 89, 45% by mass of hydrogen ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 150, and 10% by mass of γ-alumina; the composition of the obtained catalyst G is shown in Table 1, and the physical properties are shown in Table 2.

[0073] Example 8

[0074] The catalyst was prepared according to the method of Example 1, except that in step (a) of step (1), a NaOH aqueous solution with a concentration of 0.5 mol / L was used instead of a NaOH aqueous solution with a concentration of 0.3 mol / L to obtain a cylindrical strip-shaped composite support h, which contains 45% by mass of hydrogen-form ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 150, 45% by mass of hydrogen-form ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 100, and 10% by mass of γ-alumina. The composition of the obtained catalyst H is shown in Table 1, and the physical properties are shown in Table 2.

[0075] Comparative Example 1

[0076] (1) Preparation of cylindrical strip composite carrier

[0077] Take 13.4 g of pseudoboehmite, 45 g of hydrogen-form ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 89, and 45 g of SiO2. 2 / A hydrogen-form ZSM-48 zeolite with an Al2O3 molar ratio of 100 was mixed thoroughly, and then 10 grams of a 1.5% by mass nitric acid aqueous solution were added. After thorough stirring, the mixture was kneaded three times on an extruder and extruded into strips. The extruder die had a diameter radius of 0.5 mm. The extruded cylindrical strips were transferred to 60°C and dried for 4 hours, then dried at 120°C for 4 hours, and finally calcined at 550°C for 4 hours. After cooling to room temperature, the long cylindrical strips were cut into cylindrical strips with a length of 2 mm, resulting in cylindrical strip composite carrier i. This composite carrier i contains 45% by mass of hydrogen-form ZSM-22 molecular sieve with a SiO2 / Al2O3 molar ratio of 89, 45% by mass of hydrogen-form ZSM-48 molecular sieve with a SiO2 / Al2O3 molar ratio of 100, and 10% by mass of γ-alumina.

[0078] (2) Preparation of catalyst

[0079] 45 g of the composite support i prepared in step (1) was placed in 37.5 g of chloroplatinic acid (produced by Bailingwei Company) solution with a platinum concentration of 0.6% by mass and impregnated at 25°C for 3 hours. The impregnated solid was dried at 120°C for 6 hours, calcined at 500°C for 4 hours, and reduced in a hydrogen atmosphere at 450°C for 3 hours. The volume hourly space velocity of the hydrogen treatment was 5 h⁻¹. -1 The composition of the obtained catalyst I is shown in Table 1, and its physical properties are shown in Table 2.

[0080] Comparative Example 2

[0081] The catalyst was prepared according to the method of Comparative Example 1, except that in step (1), 90 g of hydrogen-form ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 89 was added instead of 45 g of hydrogen-form ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 89 and 45 g of SiO2 / Al2O3. 2 / A cylindrical strip-shaped composite support j was obtained by using hydrogen-form ZSM-48 zeolite with an Al2O3 molar ratio of 100. The support j contained 90% by mass of hydrogen-form ZSM-22 molecular sieve with a SiO2 / Al2O3 molar ratio of 89 and 10% by mass of γ-alumina. The composition of the catalyst J is shown in Table 1, and the physical properties are shown in Table 2.

[0082] Comparative Example 3

[0083] The catalyst was prepared according to the method of Comparative Example 1, except that (1) 90 g of hydrogen-form ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 100 was added instead of 45 g of hydrogen-form ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 89 and 45 g of SiO2 / Al2O3. 2 / A cylindrical strip-shaped composite support k was obtained by using hydrogen-form ZSM-48 zeolite with an Al2O3 molar ratio of 100. The support contained 90% by mass of hydrogen-form ZSM-48 molecular sieve with a SiO2 / Al2O3 molar ratio of 100 and 10% by mass of γ-alumina. The composition of the catalyst K is shown in Table 1, and the physical properties are shown in Table 2.

[0084] Comparative Example 4

[0085] The catalyst was prepared according to the method of Comparative Example 1, except that in step (1), hydrogen-form β-zeolite with a SiO2 / Al2O3 molar ratio of 2:1 was used instead of SiO2. 2 / A cylindrical strip-shaped composite support l was obtained by using hydrogen-form ZSM-48 zeolite with an Al2O3 molar ratio of 100. The support contained 45% by mass of hydrogen-form ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 89, 45% by mass of hydrogen-form β zeolite with a SiO2 / Al2O3 molar ratio of 21, and 10% by mass of γ-alumina. The composition of the catalyst L is shown in Table 1, and the physical properties are shown in Table 2.

[0086] Comparative Example 5

[0087] The catalyst was prepared according to the method of Example 1, except that in step (c) of step (1), the hydrogen form ZSM-22 and ZSM-48 mixed zeolite after alkali treatment and ammonium exchange was not acid treated, and was directly extruded, dried and calcined in step (2) to obtain a cylindrical strip-shaped composite support m, which contains 45% by mass of hydrogen form ZSM-22 zeolite with a SiO2 / Al2O3 molar ratio of 150, 45% by mass of hydrogen form ZSM-48 zeolite with a SiO2 / Al2O3 molar ratio of 100 and 10% by mass of γ-alumina. The composition of the catalyst M is shown in Table 1 and the physical properties are shown in Table 2.

[0088] Comparative Example 6

[0089] The catalyst was prepared according to the method of Example 1, except that in step (a) of step (1), a 0.7 mol / L NaOH aqueous solution was used instead of a 0.3 mol / L NaOH aqueous solution to prepare a cylindrical strip-shaped composite support n. This support contained 45% by mass of hydrogen-form ZSM-22 molecular sieve with a SiO2 / Al2O3 molar ratio of 89, 45% by mass of hydrogen-form ZSM-48 molecular sieve with a SiO2 / Al2O3 molar ratio of 100, and 10% by mass of γ-alumina. The composition of the resulting catalyst N is shown in Table 1, and its physical properties are shown in Table 2.

[0090] Table 1

[0091]

[0092] *Calculated based on the carrier. **Silicon / aluminum ratio is the molar ratio of SiO2 / Al2O3.

[0093] Table 2

[0094]

[0095] Example 9-16

[0096] Using n-heptane as a raw material, the catalyst AH of this invention was charged into a small fixed-bed reactor for isomerization reaction. The reaction conditions were: temperature 280℃, pressure 0.4 MPa, hydrogen-to-oil volume ratio of 5, and feed mass hourly space velocity (WHSV) of 1.0 h⁻¹. -1 The reaction time was 48 hours. The catalysts used in each example and the reaction results are shown in Table 3.

[0097] Comparative Examples 7-12

[0098] Isomerization was carried out using n-heptane as a feedstock in a small fixed-bed reactor with a comparative catalyst IN. The reaction conditions were: temperature 280℃, pressure 0.4 MPa, hydrogen-to-oil volume ratio of 5, and feed mass hourly space velocity (WHSV) of 1.0 h⁻¹. -1 The reaction time was 48 hours. The catalysts used in each comparative example and the reaction results are shown in Table 3.

[0099] Table 3

[0100]

[0101] Table 3 lists single-branched isoheptane isomers including 2-methylhexane, 3-methylhexane, and 3-ethylpentane; and multi-branched isoheptane isomers including 2,2-dimethylpentane, 2,3-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane, and 2,2,3-trimethylbutane. Cracking products include various isomers of C3-C4 alkanes.

[0102] As shown in Table 3, the catalyst of the present invention can achieve a higher total yield of heptane isomers, especially the yield of multi-branched heptane isomers, and a lower yield of cracking products compared with the comparative catalyst.

[0103] Example 17

[0104] This example examines the stability of the catalyst of the present invention.

[0105] Catalyst C was loaded into the reactor of a small fixed-bed reactor, using n-heptane as feedstock, at a reaction temperature of 280℃, a pressure of 0.4 MPa, a hydrogen-to-oil volume ratio of 5, and a feed mass hourly space velocity of 1.0 h⁻¹. -1 The reaction was carried out continuously for 120 hours under the specified conditions, and the results are shown in Table 4.

[0106] Table 4

[0107] Continuous reaction time, hours 24 48 72 96 120 Raw material conversion rate, mass % 80.0 79.9 79.8 79.6 79.5 heptane isomer selectivity, mass % 96.6 96.6 96.7 96.8 96.8 Total yield of heptane isomers, by mass % 77.3 77.2 77.1 77.0 76.9 Yield of single-branched heptane isomers, % by mass 70.0 70.0 70.1 70.0 70.0 Yield of multi-branched heptane isomers, % by mass 7.3 7.2 7.0 7.0 6.9 Cracking product yield, % by mass 2.7 2.7 2.7 2.6 2.6

[0108] As shown in Table 4, the feed conversion rate and isoheptane yield remained at a high level. The total isoheptane yield decreased from 77.3% by mass at the beginning to 76.9% by mass at the end of the reaction, with an average yield greater than 77.1% by mass. The cracking product yield remained at a low level, indicating that the catalyst of the present invention has good isomerization activity, isoheptane selectivity and reaction stability.

Claims

1. An isomerization catalyst, characterized in that, The catalyst comprises a composite support and platinum supported on the composite support. The composite support comprises 15.0-80.0% by mass of hydrogen-form ZSM-22 zeolite, 10.0-70.0% by mass of hydrogen-form ZSM-48 zeolite, and 10.0-60.0% by mass of alumina based on the composite support. The most probable pores of the catalyst exhibit a bimodal distribution with most probable pore diameters of 3.0-4.5 nm and 20.0-45.5 nm. The preparation method of the catalyst includes: (1) A step of treating ZSM-22 and ZSM-48 mixed zeolite with alkali and acid to obtain alkali and acid modified hydrogen form ZSM-22 and ZSM-48 mixed zeolite; (2) A step of preparing a composite support containing the alkali and acid modified hydrogen form ZSM-22 and ZSM-48 mixed zeolite obtained in step (1) and alumina; (3) A step of loading platinum; The (1) mentioned therein is: (a) Add the ZSM-22 and ZSM-48 mixed zeolite to the alkaline solution to make it fully contact the alkaline solution, filter it, wash the resulting solid with water and dry it; (b) The zeolite obtained in step (a) is added to the ammonium salt solution to allow it to fully contact the ammonium salt solution for ion exchange and filtration. The resulting solid is washed with water, dried, and calcined to obtain alkali-modified hydrogen-form ZSM-22 and ZSM-48 mixed zeolite. (c) The alkali-modified hydrogen form ZSM-22 and ZSM-48 mixed zeolite obtained in step (b) is added to an acid solution to make it fully contact with the acid solution. After filtration, the resulting solid is washed with water, dried and calcined to obtain alkali and acid-modified hydrogen form ZSM-22 and ZSM-48 mixed zeolite.

2. The catalyst according to claim 1, characterized in that, Based on the composite carrier, the platinum content is 0.01-2.0% by mass.

3. The catalyst according to claim 1, characterized in that, In the composite carrier, the mass ratio of hydrogen-form ZSM-22 zeolite to hydrogen-form ZSM-48 zeolite is 0.2-4.

4. The catalyst according to claim 1, characterized in that, In the composite carrier, the mass ratio of hydrogen-form ZSM-22 zeolite to hydrogen-form ZSM-48 zeolite is 0.3-3.

3.

5. The catalyst according to claim 1, characterized in that, The SiO2 / Al2O3 molar ratio of the hydrogen-form ZSM-22 zeolite is 20-200, and the SiO2 / Al2O3 molar ratio of the hydrogen-form ZSM-48 zeolite is 50-300.

6. The catalyst according to claim 1, characterized in that, The catalyst has a mesoporous pore volume of 0.25-0.80 cm³. 3 / g.

7. The catalyst according to claim 1, characterized in that, The catalyst has a mesoporous pore volume of 0.30-0.60 cm³. 3 / g.

8. The catalyst according to claim 1, characterized in that, The most probable pores of the catalyst exhibit a bimodal distribution, with pore sizes of 3.2-4.0 nm and 22.0-44.5 nm.

9. The catalyst according to claim 1, characterized in that, The total specific surface area of ​​the catalyst is 220.0-280.0 m². 2 / g; mesoporous specific surface area is 60.0-150.0m² 2 / g.

10. The catalyst according to claim 1, characterized in that, The total specific surface area of ​​the catalyst is 222.5-248.0 m². 2 / g; mesoporous specific surface area is 66.5-120.0m². 2 / g.

11. The catalyst according to claim 1, characterized in that, The composite carrier is a cylindrical strip with a radius of 0.2-1.0 mm and a length of 0.5-5.0 mm.

12. A method for preparing the catalyst according to any one of claims 1-11, characterized in that, The method includes: (1) The step of treating ZSM-22 and ZSM-48 mixed zeolite with alkali and acid to obtain alkali and acid modified hydrogen form ZSM-22 and ZSM-48 mixed zeolite; (2) The step of preparing a composite carrier containing the alkali and acid modified hydrogen form ZSM-22 and ZSM-48 mixed zeolite obtained in step (1) and alumina; (3) The step of loading platinum.

13. The preparation method according to claim 12, wherein (1) is: (a) Add the ZSM-22 and ZSM-48 mixed zeolite to the alkaline solution to make it fully contact the alkaline solution, filter it, wash the resulting solid with water and dry it; (b) The zeolite obtained in step (a) is added to the ammonium salt solution to allow it to fully contact the ammonium salt solution for ion exchange and filtration. The resulting solid is washed with water, dried, and calcined to obtain alkali-modified hydrogen-form ZSM-22 and ZSM-48 mixed zeolite. (c) The alkali-modified hydrogen form ZSM-22 and ZSM-48 mixed zeolite obtained in step (b) is added to an acid solution to make it fully contact with the acid solution. After filtration, the resulting solid is washed with water, dried and calcined to obtain alkali and acid-modified hydrogen form ZSM-22 and ZSM-48 mixed zeolite.

14. The preparation method according to claim 13, wherein in (a), the method of fully contacting with the alkaline solution is stirring at a temperature of 50-90°C for 1-5 hours, and the method of drying is drying at a temperature of 80-150°C for 1-5 hours.

15. The preparation method according to claim 13, wherein in (a), the alkaline solution is selected from at least one of sodium hydroxide solution, potassium hydroxide solution, tetraalkylammonium hydroxide solution, sodium carbonate solution, potassium carbonate solution or ammonia water, and the concentration of the alkaline solution is 0.05-0.6 mol / L.

16. The preparation method according to claim 15, wherein the concentration of the alkaline solution is 0.1-0.4 mol / L.

17. The preparation method according to claim 13, wherein the mass ratio of (a), the ZSM-22 and ZSM-48 mixed zeolite to the alkaline solution is 0.01 to 0.

8.

18. The preparation method according to claim 13, wherein in (b), the ammonium salt solution is an NH4Cl or NH4NO3 solution, and the concentration of the ammonium salt solution is 0.05-4 mol / L.

19. The preparation method according to claim 13, wherein in step (b), the method of fully contacting the ammonium salt solution is stirring at a temperature of 20-90°C for 1-24 hours; the drying is carried out at a temperature of 80-150°C for 1-5 hours; and the calcination is carried out at a temperature of 450-650°C for 2-6 hours.

20. The preparation method according to claim 13, wherein the mass ratio of the zeolite obtained in steps (b) and (a) to the ammonium salt solution is 0.01-0.

6.

21. The preparation method according to claim 13, wherein in (c), the acid solution is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, trifluoroacetic acid, oxalic acid, acetic acid, citric acid, tartaric acid, and malic acid solutions, and the concentration of the acid solution is 0.05-6.0 mol / L.

22. The preparation method according to claim 13, wherein in (c), the method of fully contacting with the acid solution is stirring at a temperature of 60-200°C for 4-12 hours; the drying method is drying at a temperature of 80-150°C for 1-5 hours; and the calcination method is calcining at a temperature of 450-650°C for 2-6 hours.

23. The preparation method according to claim 13, wherein the mass ratio of the alkali-modified hydrogen-form ZSM-22 and ZSM-48 mixed zeolite obtained in steps (c) and (b) to the acid solution is 0.01-0.

8.

24. The preparation method according to claim 12, wherein step (2) is: fully mixing pseudoboehmite powder with the alkali and acid modified hydrogen-type ZSM-22 and ZSM-48 mixed zeolite obtained in step (1), adding an appropriate amount of acid solution, kneading evenly, extruding into strips, drying, and calcining to obtain a composite carrier.

25. The preparation method according to claim 24, characterized in that, The acid solution is an inorganic acid or an organic acid solution. The inorganic acid is selected from nitric acid and hydrochloric acid, and the organic acid is selected from acetic acid and formic acid. The concentration of the acid solution is 0.1-5% by mass; the mass ratio of the acid solution to boehmite powder is 0.5-2.

26. The preparation method according to claim 24, characterized in that, The number of kneading cycles is 1-5.

27. The preparation method according to claim 24, wherein the drying is first performed at a temperature of 30-100℃ for 2-6 hours, and then at 110-150℃ for 2-24 hours; and the calcination is performed at a temperature of 500-650℃ for 2-8 hours.

28. The preparation method according to claim 12, wherein step (3) is: impregnating, drying, calcining and reducing the composite carrier prepared in step (2) with a solution containing a platinum compound.

29. The preparation method according to claim 28, characterized in that, The concentration of platinum in the solution containing the platinum compound is 0.02-2.0% by mass, and the platinum compound is a chloride or nitrate of platinum.

30. The preparation method according to claim 29, characterized in that, The platinum compound mentioned is chloroplatinic acid.

31. The preparation method according to claim 28, characterized in that, The impregnation temperature is 10-50℃, the time is 1-4 hours, and the liquid / solid mass ratio is 0.5-1.

3.

32. The preparation method according to claim 31, characterized in that, The soaking time is 2-3 hours.

33. The preparation method according to claim 28, characterized in that, The drying process is carried out at a temperature of 110-150℃ for 2-24 hours; the calcination process is carried out at a temperature of 500-700℃ for 0.5-8 hours.

34. The preparation method according to claim 33, characterized in that, The roasting time is 4-6 hours.

35. The preparation method according to claim 28, characterized in that, The reduction process uses H2 as the gas, with a volume hourly space velocity (VHSV) of 1.0-10.0 h⁻¹. -1 The temperature is 400-600℃, and the time is 0.5-8 hours.

36. The preparation method according to claim 35, characterized in that, The reduction process involves a temperature of 420-500℃ and a time of 2-4 hours.

37. The catalyst obtained by the preparation method according to any one of claims 12-36.

38. An isomerization method, comprising contacting and reacting a n-alkane with a catalyst under hydrogen-containing conditions, characterized in that, The catalyst is any one of claims 1-11 and 37.

39. The isomerization method according to claim 38, wherein the isomerization conditions include: The temperature ranges from 100 to 400℃, the pressure from 0.1 to 5.0 MPa, the hydrogen-to-oil volume ratio from 0.5 to 500, and the feed mass hourly space velocity (WHSV) from 0.05 to 10.0 h⁻¹. -1 .

40. The isomerization method according to claim 39, wherein the isomerization conditions include: The temperature is 200-340℃ and the pressure is 0.2-1.0MPa.

41. The isomerization method according to claim 38, wherein the n-alkane is a C4-C12 n-alkane.

42. The isomerization method according to claim 38, wherein the n-alkane is a C6-C8 n-alkane.

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